A taxane-type anti-cancer agent is an anti-cancer agent for inhibiting division of cancer cells and inducing apoptosis and has excellent therapeutic effects by being made to contact the cancer cells in Gap2 (G2 phase) through mitosis and cytokinesis (M phase). However, the cancer cell killing effect of the taxane-type anti-cancer agent is low in Gap0 (G0 phase) and Gap1 (G1 phase) and growth of the cancer cells in the G1 phase cannot be inhibited. Moreover, when the taxane-type anti-cancer agent is administered to normal tissues, side effects such as vomiting and leukocyte decrease occur. The taxane-type anti-cancer agent is administered by providing a medication cessation period in order to inhibit the side effects.
Drug Delivery Systems (DDS) exist as a means for making the taxane-type anti-cancer agent unerringly reach affected site tissues and avoiding contact between cells constituting the normal tissues and the taxane-type anti-cancer agent. As an example of the DDS, there is a technique that uses a carrier to guide drug molecules to the affected site tissues (PTL 1). However, when the carrier is used, its molecular size increases and, therefore, an administration method is limited. Furthermore, the carrier and the drug decompose before they reach the affected site tissues; and the drug which stays in the normal tissue may sometimes cause the side effects. In such a case, that will adversely affect a patient's quality of life.
The inventors of the present disclosure suggested, in PTL 2, an anti-cancer agent which does not use a carrier. PTL 2 discloses a compound in which a drug is made to bind to a metal-salen complex compound. Since the compound disclosed in PTL 2 is self-magnetic, the carrier is not required in order to carry the drug. However, there is a demand for an anti-cancer agent which has less side effects and whose cancer cell killing effect is further enhanced. Particularly, an anti-cancer agent which exhibits the excellent effect of killing cancer cells of triple-negative breast cancer has not been discovered. The anti-cancer agent which continuously kills the cancer cells is being examined from the viewpoint of enhancement of the killing effect.